The present invention relates to video quality measurements, and more particularly to a single-ended blur detection method to determine overall sharpness of a scene in a video image sequence.
Television broadcasters are interested in determining the quality of a video image sequence that is distributed over Internet Protocol (IP) and radio frequency (RF) broadcast networks. Recently broadcasters have become concerned about the sharpness or, conversely, the blur in video image sequences. There have been customer complaints that some video image sequences look less sharp than others. Such lack of sharpness, or blurring, may be caused by over-compression due to loss of detail resulting from tiling, i.e., coarse pixelation, or de-blocking filters in H.264 compression coders/decoders (CODECs) that remove horizontal and vertical edges which typically further blurs the video image sequence. This may also be caused by up-conversion of the video image sequence, such as from a standard definition (SD) to high definition (HD) video image sequence, where pre-filtering to remove aliasing creates images that have detail below available pixel resolution of the HD video image sequence. Other sources of blurring may include noise reduction or other processing, such as defocus blur typically caused by image processing and motion blur caused by image integration due to linear or non-linear motion during shutter time, that gives an overall impression of a blurry or fuzzy video image sequence.
More and more video delivered by broadcasters is in an HD format. However, a good deal of the programming provided in the HD format originated as SD material that is up-converted. For example, 720×480 or 720×576 interlaced SD material may be up-converted to the higher resolution HD formats, such as 1920×1080 interlaced frame video or 1280×720 progressive frame video. Therefore the up-converted SD video frame content does not provide the detail or sharpness to the full potential of the HD resolution, i.e., the HD video looks soft or blurred. It would be desirable to provide a means for automatically detecting program content in HD that is most likely up-converted SD video.
Prior blur or soft image detection methods are overly sensitive to noise, such that noise within the video images reduces the assigned blur value even though the image still appears soft or blurry. It is desirable to mitigate the sensitivity of blur detection due to noise.
Also, there are many objects within an image, such as foreground and background objects and other features that may or may not be soft or blurry by nature or for artistic reasons. It is desirable to understand what objects within the image are used by any blur detection method in order to determine which objects within the image are used to determine the assessed blur value to support confidence in the assessed blur value.
What is desired is a probe or method that broadcasters may use to assess the blurriness or sharpness of a video image sequence at various distribution points in a distribution network to determine system quality with reasonable confidence.